The present invention relates to a thin film for recording, data, which is capable of recording, in real time frequency-modulated, video or audio analog signals by a recording beam such as laser beam and electron beam, or which is capable of recording, in real time, digital information such as data of an electronic computer, facsimile signals, or digital audio signals.
There have been proposed a variety of principles for recording data on a thin film using a laser beam. Among them, the recording based upon the change in the arrangement of atoms such as phase transition (or often called phase change) of a film material or photodarkening, is advantageous in that the film is deformed very little and that a double-sided disc can be obtained by directly adhering two pieces of discs. By suitably selecting the composition, furthermore, it is possible to rewrite the data. A number of patent applications have been filed in connection with the recording of this type, and the earliest invention has been disclosed in Japanese Patent Publication No. 26897/1972, which teaches many thin films of the Te-Ge system, As-Te-Ge system, Te-O system, and others. Also, Japanese Patent Laid-Open No. 41902/1979 teaches a variety of compositions such as Ge.sub.20 Tl.sub.5 Sb.sub.5 Se.sub.70, Ge.sub.20 Bi.sub.10 Se.sub.70, and the like. Furthermore, Japanese Patent Laid-Open No. 24039/1982 discloses thin films composed of Sb.sub.25 Te.sub.12.5 Se.sub.62.5, Cd.sub.14 Te.sub.14 Se.sub.72, Bi.sub.2 Se.sub.3, Sb.sub.2 Se.sub.3, In.sub.20 Te.sub.20 Se.sub.60, Bi.sub.25 Te.sub.12.5 Se.sub.62.5, CuSe, and Te.sub.33 Se.sub.67 When the film is to be used as a phase transition recording film which permits the data to be written one time or which permits the data to be rewritten, however, the above-mentioned thin films are defective in that they exhibit a slow speed of crystallization, that they absorb little of the semiconductor laser beam and exhibit poor sensitivity, that they reproduce signals of insufficient intensity, that their amorphous state lacks stability, and that their resistance against oxidation is not sufficient. It is, therefore, difficut to put the above-mentioned thin films into practice.